West Nile’s record season has residents concerned about fogging

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A dead crow from River Glen Park awaits testing for West Nile Virus at the Santa Clara County Vector Control laboratory in San Jose, Calif., Wednesday morning July 2, 2014. (Karl Mondon/Bay Area News Group)

The Santa Clara County Vector Control keeps a sentinel flock of chickens to help monitor the spread of West Nile Virus cases in San Jose, Calif., Wednesday morning July 2, 2014. (Karl Mondon/Bay Area News Group)

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A map at the Santa Clara County Vector Control indicates the growing number crows found to have West Nile Virus in San Jose, Calif., Wednesday morning July 2, 2014. (Karl Mondon/Bay Area News Group)

The Santa Clara County Vector Control keeps a sentinel flock of chickens to help monitor the spread of West Nile Virus cases in San Jose, Calif., Wednesday morning July 2, 2014. (Karl Mondon/Bay Area News Group)

Michael Stephenson logs in a dozen dead crows being tested for West Nile Virus at the Santa Clara County Vector Control laboratory in San Jose, Calif., Wednesday morning July 2, 2014. (Karl Mondon/Bay Area News Group)

Two dead crows await testing for West Nile Virus at the Santa Clara County Vector Control laboratory in San Jose, Calif., Wednesday morning July 2, 2014. (Karl Mondon/Bay Area News Group)

SAN JOSE — A murder of crows blackened the spotless white examination table — a dozen gape-beaked birds, each in its own zip-locked body bag, tagged and ready for testing one recent day.

Their deaths weren’t much of a mystery: Vector control workers immediately identified the primary suspect that knocked the crows from their perches, a prediction that came true when the first results arrived minutes later. Crimson streaks that appeared on test strips confirmed suspicions that West Nile virus had struck again.

“We’re seeing more than in all the other years,” said Mike Stephenson, the disease surveillance specialist with Santa Clara County Vector Control who swabbed the beaks of the crows to check for the deadly virus, which is carried by mosquitoes and also poses tremendous risk to humans.

“We’ve had other busy years, but not like this.”

As of July 10, the county logged 286 infected birds; that’s nearly 60 percent of the positives counted statewide and more than three times the number found in all of 2013. At this time last year, positive hits could be counted on one hand. Once the birds’ infection is confirmed, workers then seek to zero in on infected mosquitoes, which are more difficult to track.

Local and state officials can’t pinpoint a reason for the high numbers, but they are worried about what the dead birds portend for the county’s residents. The California Department of Public Health cited conditions such early warm temperatures and a lack of rainfall as possible boosters.

“That certainly seems to be one of the factors,” county vector manager Russ Parman said of the drought. He said that while it seems counterintuitive — less water should mean less mosquito breeding — it actually has the opposite effect.

“Birds and mosquitoes are in closer contact because they come together at the same watering holes,” Parman said.

Fogging worries

Whatever the reasons, Santa Clara County stands out among neighbors. San Mateo County found its first infected bloodsucker in years, which resulted in a mosquito fogging last month. Contra Costa County has seen 10 dead birds and one infected mosquito sample and fogged twice this year. In Alameda County, which hasn’t fogged in 15 years, five infected birds have been found and no mosquitoes.

By contrast, Santa Clara County is on track to easily surpass last year’s record 13 foggings, with the 10th taking place Thursday. The trigger to bring out the chemicals is a positive virus hit in a mosquito — the only way to kill the adults is through the spraying — and they’ve been getting those hits this year, with 16 so far. Sacramento County has had the most statewide: 76. But at this time last year, there were none in Santa Clara County.

The increased fogging doesn’t sit well with some residents, who have shown up to county meetings to voice their concerns about truck-mounted misters spewing poison through their neighborhoods in the dead of night.

“I’d like to know who is advising the county that spraying is worth it,” said Jennifer Schmid, a nurse who lives in Sunnyvale. “This stuff is so toxic. Where’s the cost-benefit risk analysis?”

That “stuff” used in fogging operations is pyrethroid. Parman said the pesticide has been studied extensively and is a less toxic, synthetic version of the chrysanthemum-based pyrethrin commonly found in dog and cat flea shampoos. He also said that in 30 years of fogging, there hasn’t been a documented case of the spray harming anyone.

“It’s not known for knocking out anything bigger than a housefly,” he said. “We know more about these products going out than we do of what’s sold over the counter as herbal remedies.”

Schmid and others believe that known and unknown adverse effects of pesticides such as the pyrethroid outweigh what they call a rare and usually not-so-severe human West Nile infection. Just over 4,000 cases have been documented in humans statewide since the disease appeared in 2003, with 145 fatalities. Nineteen of those cases were from Santa Clara County, with two last year, although none of those people died. In the Bay Area, Contra Costa County historically has seen the most, with 47 diagnosed cases and two fatalities, both in 2006. Nine human cases have been reported statewide this year, three in both Stanislaus and Tulare counties and one each in Fresno, Solano and Contra Costa counties.

But Deborah Bass of Contra Costa County Mosquito and Vector Control said, “West Nile virus is grossly underreported.” She cited a Centers for Disease Control study that showed for every person diagnosed with a severe case, 70 more may have thought they’d just had a nasty bout with the flu.

“We estimate, based on the CDC data, that as many as 350 people had West Nile virus last year in Contra Costa County,” Bass said. “They just didn’t know it or it wasn’t tested for or reported.”

Vector control officials say the virus isn’t something to sneeze at.

“Even its mild form averages 16 days off work,” Parman said. “It’s not the common cold. And for a small percentage it gets neuroinvasive — we’re talking encephalitis. It’s a very significant disease.”

Pesticide paradox

Fogging opponents cite studies that show pesticide exposure can lead to respiratory and neurological disorders; a recent UC Davis study linked use of pyrethroids in agricultural fields with increased incidence of autism in children whose mothers were exposed while pregnant.

“The effect was very mild, and by no means does it show pesticides cause autism — it’s one of many risk factors,” said Alycia Halladay, senior director of environmental and clinical sciences with the Autism Speaks advocacy group. “But pesticides are chemicals that are known to be toxic, and if you can control the amount you are exposed to, you should — especially pregnant women.”

Halladay said that as far as a risk assessment, the situation is a paradox.

“We don’t know what effect West Nile virus has during pregnancy,” she said. “On the other hand, you want to avoid pesticides because there’s a small increased risk of having a child with autism after exposure. It’s damned if you do, damned if you don’t.”

Get rid of standing water around the home. This could be in buckets, old tires, flower pots and toys.

Water in bird baths and pet bowls should be changed every few days. It takes a week for a mosquito egg to hatch and grow into an adult.

Make sure screens on windows and doors are secure. Properly attached, they will keep mosquitoes out.

Avoid being bit when out by taking proper precautions. Mosquitoes bite in the early morning and early evening, with the prime time two hours after the sun sets. Wear long pants and long sleeves during these hours, and put insect repellent on exposed skin.

To report a dead bird or squirrel, call the West Nile Virus Hotline at 877-WNV-BIRD (968-2473) or online at westnile.ca.gov. Be prepared to give the location, animal description, when it was first seen and its condition.

Eric Kurhi is a reporter for the Bay Area News Group based at The Mercury News. He covers Santa Clara County government and general assignment duties. An East Bay native, he has been editing and reporting at local newspapers since graduating from San Francisco State University in 1997.

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